Manufacture of filaments, films, or the like of artificial materials



T. F. BARRINGTON MANUFACTURE OF FILAMENTS, FILMS OR THE LIKE 0F ARTIFICIAL MATERIALS Filed Dec.

Feb. 2% E951 Patented Feb. 20, 1951 MANUFAUIURE OF FILAMEN TS, FILMS, OR THE LIKE OF ARTIFICIAL MATERIALS Tom Barrington, Alderwasley, England, as-

signor to Slack & Parr Limited, Kegworth,

England Application December 2, 1947, Serial No. 789,173 In Great Britain December 7, 1946 Claims. 1

This invention relates to the manufacture of filaments, such as continuous threads, films, strips or hands, of artificial materials. It is particularly concerned with the production of continuous filaments from solutions or suspensions of cellulose derivatives, such as a mixture of acetate-esters of cellulose.

In the production of acetate silk filaments, films or the like the solution or suspension in the spinning bath or casting box is forced by gravity or other means through an orifice of the required dimensions after which the viscous filaments, films or the like are set or solidified by evaporating the liquid in which the cellulose derivative is dissolved or suspended. Such evaporation is carried out by subjecting the filaments as they leave the spinning nozzle (or the films issuing from the slit-like orifice) to the action of heat and a current of dry air.

As the process is continuous, the drying operation has to be effected rapidly and in practice warm, dry air is employed in countercurrent to the filaments issuing from the orifice of the spinneret. process it is also customary to pass the filaments, films or the like through an exhausted chamber to effect evaporation of the acetone solvent as rapidly as possible, the filaments, films or the like being heated by radiation whilst passing through the chamber.

This method of dryin is not entirely satisfactory and it is found that, although the outside of the filaments, films or the like can be dried rapidly, the inside remainswet with consequential disadvantageous results in the subsequent winding and/ or yarn-forming operations. Two of such disadvantages in the case of filaments are that the filaments tend to become collapsed, almost hone shaped in cross-section, instead of truly circular and that there is loss of acetone by that amount trapped in the filament.

The main objects of the present invention are to avoid these defects in filament manufacture, to speed up the production of films and generally to provide an improved method of and apparatus for manufacturing acetate silk.

Another object is to provide a method of manufacturing filaments for example threads, films or the like in continuous lengths, of artificial materials in which a spinning solution or suspension, is forced through a spinning orifice to produce the filaments, which are subjected as they issue from the spinning orifice to the action of a radio frequency electrostatic field so applied With a view to expediting the drying as to cause substantially evendrying of the filaments throughout their section.

If desired, the member in which the spinning orifice is formed and the winding device or guide receiving the filaments from the spinning orifice themselves form heating electrodes supplied with radio frequency energy. Thus, the lines of force are concentrated along the filaments or films instead of running transversely thereto, whereby the maximum heating effect in the filaments is obtained. According to another feature of the invention the filaments, films or the like are subjectedto th action of the radio frequency electrostatic field while passing through a saturated 61' supersaturated atmosphere of acetone or other suitable solvents. The filaments, films or the like preferably issue from the spinning orificeimmedh ately-into the said supersaturated atmosphere so that no initial rapid drying of the outside surface of the filaments, films or the like can take place before the application of the radio frequency heating. By this means substantially even drying of the filaments, films or the like from their centres takes place so that the tendency to collapse of the filaments or films is completely avoided. 1

Apparatus for carrying the invention into effeet will now be described, by way of example, with reference to the accompanying drawings, in Which-- Figure 1 is a part sectional diagrammatic view of cellulose spinning apparatus for the manufacture of acetate filaments showing only the parts necessary to illustrate the invention, and

Figures 2, 3 and 4 are diagrammatic sectional views of the cabinet shown in Figure l illustrating alternative methods of subjecting the filaments to the radio frequency electrostatic field.

Referring to Figure 1, the spinning solution from the casting box is pumped through a spinning orifice in the form of a multiple spinneret --I 2 by a metering pump It, the solution being fed tothe spinneret through a conduit 34 and filter II. The multiplicity of wet filaments I! issuing from the spinneret [2 are simultaneously and continuously drawn by a winding device 23 through a cabinet l3, having the spinneret l2 centrally disposed near its upper end. Heat is generated in the filaments as they pass through the cabinet It by an electrostatic field which is supplied from a source of radio frequency energy 20. The latter is connected to the spinneret i2 and a guide or other device l8 over which the atmosphere of acetone.

radio frequency energy 20 by a lead 2|. "ond lead '22 conveys positive potential to the from the guide I8 to the spinneret l2, andare substantially parallel to the path of the filaments I'I'. By using quite moderate powersjalmost instantaneous drying of the filaments is obtained right to theircentres so that the filaments may be wound, combined to form yarn or su-bjected to any other desired process without having to allow drying time.

To prevent initial rapid drying of the outside surface of the filaments I'I, it may be necessary to keep the cabinet I3 constantly charged during the spinning process with a non-drying atmosphere, for example a saturated or supersaturated This may be accomplished by injection or other means in the form of a nozzle 33 mounted in the wall of the cabinet I 3 for the purpose. Such injection may'only be necessary during the initial stages of the spinning process, a'saturated atmosphere being thereafter maintained in the cabinet I3 by evaporation-of the acetone or like solvent from the fila- I4 for draining off the liquid acetone condensing in the cabinet which passes through the tube and is continuouslycollected in a tank l5.

"Owing to difficulties in securing insulation of the cabinet I 3 and the metering pump I and n1- "ter 1 I, it preferred to connect the spinneret (2 to the negative or earth side of the source of A secguide I8. To prevent the filaments I'I being drawn on to the winding device 23 in a positively charged condition after contact with the 7 guide I8, "a further guide I9 is interposed betwe'en them. This is connected to "the negative side of the source of radio frequency energy 2|] by an extension of lead 2|, the filaments I! being earthed by contact with this guide.

latter and the spinneret I2 and connected to'thepositive side of the source of radio frequency energy by a lead 22. A second guide 25 is provided outside the cabinet l3 nea'r'the aperture I6 and connected to the'ne'gativ'e side or thesource of radio frequency energy 20 which is "also conriected to the spinneret I2. In this'example the electrostatic field between the spinneret l2 and the insulated guide 24 is confined within the cabinet and is substantially parallel to the path of the filaments 11.

Figure 3 illustrates another method-of applying radio frequency energy to the filaments. In this case spaced heating electrodes 26 and 21 are disposed inside'the cabinet wand define a enamel between tue-spinneret l2 and the aperture H5 in the base of the cabinet. One elec trode 26 is connected to the positive side of the source of radio frequency energy by a lead 22 whilst the other 2'! is connected to the negative side by a lead 2|. In this example the electrostatic :field lies in a transverse plane to the filaments H which are drawn from the .spinneret I2 through the chamber I3, emerging therefrom through the aperture l6 and over a guide 28 on to the winding device 23.

Figure 4 illustrates a method of heating the filaments IT by radio frequencies in the microwave regions. The cabinet I3 is charged with a "saturated or supersaturated atmosphere of acetone as before and a cavity resonator 29 is axially disposedin the cabinet so that the filaments 11 pass 'therethrough and emerge through the aperture I6. Microwaves are conveyed from the source of radio frequency energy to the cavity resonator by a wave guide 30 passing through the side of the cabinet 13. A guide 3 is proviaedat the base oi the cabinet I3 over which the filaments H are drawn by the winding device in the foregoing examples the cabinet I3 may be fitted with a sliding or hinged door (not illustrated) which provides access to the spinneret I2 for cleaning purposes. If desired the cabinet may be composed largel of transparent materialto enable the spinning process to be watched.

By means of the invention, the drying time for cellulose acetate filaments, films or the like is'r'educed to a fraction of the time normally occupied and the length of run of the filaments 'or' 'films'bc'tween'the spinneret l2 and the guide -I8 may therefore be correspondingly reduced. 'The'c'abinet I3 is thus of considerably less height than usual with consequential saving in space, maintenance and the like. Moreover, filaments o'rffilms of the desired even cross-section are obtained with consequential increase in value of the yarns produced from the filaments.

I-claim:

'1. method of manufacturing continuous filament's of artificial materials, comprising extrudin'g a spinning solution containing cellulose denatives-through a spinning orifice directly into an i'solated'spa'ce constantly charged with a nondrying atmosphere to prevent initial rapid drying of the outside surface-dfthe extruded products and'siibjecting said products whilst in's'aid isolated space to the action of a radio frequency electrostatic field to cause substantially even (if the extrudedpre'ducts' from their cenres.

"2. A method of manufacturing continuous filaments of artificial materials, comprising extruding a'spinning solution containing cellulose acetate t'nreugh a spinning orifice immediatel into anisciateaspace constantly charged with a nondrying atmosphere to prevent initial rapid drycrtne outside surface of the extruded prodiicts whilst in said isolatedspace and simultaneouslysiibjecting said products to the action of a radioffreqiiency'electrostatic'fieldto cause substantially even drying of the extruded products from their centres.

-3. A method according to claim 2, wherein the non dry ing atmosphere comprises a saturated atmosphere or acetone, the condensed acetone being continuously collected from the isolated space.

'4uAnappa1-atus for manufacturing art ficial materials "from scl'utidris of cellulose derivatives comprising a spinning cabinet, a spinneret in said cabinet, injection means for constantly charging said spinning cabinet with a non-drying atmosphere to prevent initial rapid drying of the outside surface of the extruded products, and means for setting up a radio frequency electrostatic field in said cabinet.

5. An apparatus according to claim 4, wherein said means for setting up a radio frequency electrostatic field comprise a cavity resonator axially disposed in the spinning cabinet, a source of radio frequency energy and a wave guide to convey microwaves from said source of radio frequency energy to said cavity resonator.

6. An apparatus according to claim 4, wherein a guide is provided for said artificial materials and said means for setting up a radio frequency electrostatic field in said cabinet comprise a source of radio frequency energy one pole of which is connected to said spinneret whilst its opposite pole is connected to said guide.

7, An apparatus according to claim 4, wherein a guide is provided for said artificial materials and said spinneret is arranged at one end of the spinning cabinet and said guide is arranged near its opposite end adjacent an aperture.

8, An apparatus according to claim 4, wherein a guide is provided for said artificial materials and said spinneret is arranged at one end of said spinning cabinet and said guide is disposed within the spinning cabinet, a second guide being arranged outside the spinning cabinet at the end of the latter opposite to that at which said spinneret is arranged, said second guide being adjacent an aperture formed in said opposite end.

9. An apparatus according to claim 4, wherein said means for setting up a radio frequency electrostatic field in said cabinet comprise spaced heating electrodes parallelly arranged within said spinning cabinet which define a channel through which said artificial material passes and a source of radio frequency energy connected to said heating electrodes.

10. An apparatus according to claim 4, comprising means for continuously collecting the liquid formed by condensation in the spinning cabinet.

TOM F. BARRINGTON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,906,042 Barthelemy Apr. 25, 1933 2,068,538 Dreyfus et a1 Jan. 19, 1937 2,168,027 Gladding Aug. 1, 1939 2,185,417 Norton Jan. 21, 1940 2,303,983 Brown Dec. 1, 1942 2,433,842 Grifiin Jan. 6, 1948 OTHER REFERENCES Product Engineering article Engineering Abstracts, January 1947, pages 137 to 140. 

4. AN APPARATUS FOR MANUFACTURING ARTIFICIAL MATERIALS FROM SOLUTIONS FO CELLULOSE DERIVATIVES COMPRISING A SPINNING CABINET, A SPINNERET IN SAID CABINET, INJECTION MEANS FOR CONSTANTLY CHARGING SAID SPINNING CABINET WITH A NON-DRYING ATMOSPHERE TO PREVENT INITIAL RAPID DRYING OF THE OUTSIDE SURFACE OF THE EXTRUDED PRODUCTS, AND MEANS FOR SETTING UP A RADIO FREQUENCY ELECTROSTATIC FIELD IN SAID CABINET. 